French pharmaceutical giant Sanofi has said it is suing US rival Eli Lilly in an American court for infringing four patents relating to its diabetes treatments.
The lawsuit, lodged in the state of Delaware, was triggered by Eli Lilly's notification last month that it plans to ask the US Food and Drug Administration (FDA) for permission to put a new diabetes treatment on the market.
"Sanofi announced today (Thursday) that it filed a patent infringement suit against Eli Lilly and Company," the French company said in a statement.
Sanofi is seeking to protect its insulin drug Lantus and insulin pen Lantus SoloStar, which generate a sixth of the company's sales.
Eli Lilly is challenging Sanofi patents listed for Lantus and has stated that it will not launch its own product before the expiry of Sanofi's patent on the drug's active ingredient, which is in force until mid-February 2015, Sanofi said in its statement.
Mark Clark, analyst at Deutsche Bank, said the lengthy legal process begun by Sanofi would probably delay Eli Lilly's launch of the drug to market until at least 2016.
An Eli Lilly spokesman told AFP it was studying the complaint and had no immediate comment.